We propose to carry out a randomized controlled treatment trial in patients with Reye's Syndrome (RS). The treatment of RS is empirical and varies from hospital to hospital. Since the cause of this illness is unknown, the only effective means to prove efficacy of treatment modalities is to subject them to randomized trials. The incidence of RS is different from year to year and also in its geographic distribution. The number of cases of RS seen at any one center is quite low. In order to have enough patients, in all regions of the country and spaced over several years we have established a national team of RS investigators. This group working together has devised a treatment protocol to study the effectiveness of two means of controlling elevated intracranial pressure in comatose children with RS. Patients will be randomized into either standard intensive care support with mannitol osmotherapy (X), or this same treatment plus pentobarbital induced coma (Y). An organizational structure has been developed to supervise the project, manage the data, analyze the data and maintain open channels of communication. The operational office as well as the Data Coordinating Center and Neuropsychological Management Office will be at the Medical College of Virginia. Three regional directors will interface between the central offices and the local treatment centers. A team of nurses one each assigned to the national and regional offices will assist in the operations of the study, serve as liaisons between medical and nursing personnel and standardize nursing care. The National Nurse Coordinator will also link the Data Coordinating Center and the local investigators. A center for review of neurological information has been set up at East Carolina University. Meetings and site visits will ensure optimal collaborative spirit and allow for the rapid dissemination of new information. A central specimen storage facility will be set up at the University of California, San Francisco. Tissues will be transported their and stored for future investigations.